Fuel injection pump for internal combustion engines

ABSTRACT

A fuel injection pump for internal combustion engines which has a supply volume adjusting mechanism, being adjustable via a starting lever, an adjusting lever, and a tensioning lever. The starting lever is supported on the tensioning lever via a starting spring, and at non-operation of the engine, the starting spring is supported on a lever stop. To set the optimum amount of fuel to be injected at starting of the engine, which must be reduced at hot start, as opposed to a cold start, the lever stop is forcibly coupled with the adjusting lever such that the lever stop is moved by a swivel movement of the adjusting lever from a first end position to a second end position with the end positions being arranged so that the lever stop forces a starting lever position which in the first end position sets an amount of fuel on the supply volume adjusting mechanism as required for the hot start, and in the second end position, the lever stop sets an amount of fuel as required for the cold start.

STATE OF TECHNOLOGY The invention is based on a fuel injection pump forinternal combustion engines of the type defined hereinafter.

To avoid any fume bursts from the exhaust on hot start, it is necessarywith Diesel engines to reduce the amount of fuel which the fuelinjection pump has metered for a cold start.

To overcome this problem, in a known fuel injection pump of theaforementioned type (DE 28 44 910 A1) the lever stop which determinesthe start position of the starting lever is displaced, depending on thetemperature of the internal combustion engine, so that as thetemperature rises, it shifts the starting lever in the direction of thesetting for smaller fuel injection volumes. The supply volume adjustingmechanism, which is moveable on the fuel injection pump plunger, movesin relation to the starting lever position, this mechanism determinesthe amount of the plunger stroke, and hence the apportioned volume ofinjected fuel. The lever stop is moved by means of an expansion devicecontroller, which projects into a chamber through which the enginecooling water flows and which engages the lever stop via a Bowden cable.When the engine is hot, the lever stop can be set to only one position,which corresponds to the full load position, but not lower than thisposition. This means that the warm start will not be entirely free fromexhaust fume bursts. Moreover, such an adjusting device is fairlyelaborate technically, and requires considerable additional costs in itsmanufacture.

ADVANTAGES OF THE INVENTION

In contrast, the fuel injection pump of the invention with the featuresset forth has an advantage that the different volumes required for hotand cold starts, can be set with very little effort. This simplyrequires a gear-type linkage between the adjusting lever and lever stop,such that by the swivelling movement of the adjusting lever, which isactuated by the accelerator pedal, the lever stop is moved from one endposition to the other. Depending on the starting conditions (cold or hotstart), the driver must, or must not, actuate the accelerator pedal, sothat the starting lever will always assume the correct end position.

Further advantageous developments and improvements of the fuel injectionpump described are possible through the actions listed hereinafter.Where in accordance with a preferred embodiment of the invention thelever stop is coupled with the adjusting lever in such a way that with anon-actuated adjusting lever, it assumes the first end position, then astarting sequence which is logical to the driver, is achieved: if theengine is cold, the driver must actuate the accelerator pedal, if theengine is hot, he must not actuate the accelerator pedal.

According to an embodiment of the invention, the coupling between leverstop and the adjusting lever is effected by means of a setting leverwhich is located torsionally rigid on the rocking shaft of the leverstop, and is actuated by the adjusting lever. The two end positions ofthe lever stop are determined by fixed stops in the swivel path of thesetting lever. This has the advantage that the adjusting lever locatedoutside the pump housing can be easily coupled with the lever stop whichis arranged in the pump housing, without interference with the pumphousing. The setting lever is also arranged outside the pump housing.

According to a further embodiment of the invention, the setting lever isarticulated on the adjusting lever via a spring damped linkage. This hasthe advantage that the end positions of the setting lever and of thelever stop, respectively, and hence the start positions of the startinglever, can be set independently of the adjustment path of the adjustinglever. When the accelerator pedal is actuated, irrespective of theamount of pedal movement, then, after a minimum swivel movement of theadjusting lever, the setting lever will be in contact with the stopwhich defines the second end position, and it will retain this positioneven during further swivel movement of the adjusting lever.

For adjustment of the desired fuel starting volume, according to afurther embodiment of the invention, the two stops of the adjustinglever are designed on adjusting screws in such a way that the endpositions can be set with high accuracy.

DRAWING

An embodiment example of the invention is shown in the drawing and isdescribed below in more detail. The drawing shows in:

FIG. 1 a section of a side view of a fuel injection pump, and

FIG. 2 a top view of the fuel injection pump in FIG. 1.

DESCRIPTION OF THE EMBODIMENT EXAMPLE

In the sectional view of the fuel injection pump, shown in side and topelevation, the pump housing is indicated by a dash-dot line and isnumbered 10. The internal construction of the fuel injection pump isknown and described, for example in the DE 28 44 910 A1. Of thecomponents arranged inside the pump housing 10, only those shown by adash-dot line are needed for the full comprehension of the invention,namely a delivery volume adjusting mechanism 11, which is locatedaxially movable on a pump plunger 12 and which closes a delivery orificein the pump plunger 12, a two-arm starting lever 13 which is pivotedabout an axis 14, this starting lever engaging on the pump plunger 12, asingle-arm tensioning lever 15 which is pivoted about the axis 14, onwhich the starting lever 13 is supported via a starting spring 16, and alever stop 17, which is located torsionally rigid on a shaft 18 mountedin the pump housing 10. When the engine is not operating, the tensioninglever 15 contacts the lever stop 17 via a tensioning spring 35 on aspring plate 19 of a controller linkage 34, which is only implied in theillustration, and the starting lever 13 contacts the same lever stop 17under the effect of the starting spring 16. Although not shown indetail, the tensioning lever 15 is connected, via an idling and controlspring and the controller linkage 34, with an adjusting lever 20 whichis pivoted at point 21 on the outside of the pump housing 10 and whichcan be pivoted arbitrarily via the accelerator pedal in the direction ofthe arrow 22 (FIG. 2). With a non-actuated accelerator pedal, theadjusting lever 20 will assume its position shown in FIGS. 1 and 2. Afurther item not shown is the flyweight speed governor which is incontact with the starting lever 13 and which effects a shift of thedelivery volume adjusting mechanism 11, via this starting lever and thetensioning lever 15, which is appropriate to the operating conditions ofthe internal combustion engine. The delivery volume adjusting mechanism11 determines in a known way, the amount of fuel injected into thecylinders by the fuel injection pump, by virtue of the delivery orificeemerging from the delivery volume adjusting mechanism 11 after a pumpplunger stroke which is governed by the position of the delivery volumeadjusting mechanism, and a return flow is enabled for the fuel stillpresent in the pump working chamber.

The shaft 18 projecting outwards from the pump housing 10 has a settinglever 23 connected to it, so as to be torsionally rigid on the outsideof the pump housing 10, this lever 23 is coupled with the adjustinglever 20 via a spring damped linkage 24. This consists of a rod 25 whichis eccentrically pivoted on the adjusting lever 20, and a helicalcompression spring 26 within which the rod 25 is concentricallyenclosed. The rod 25 projects through a hole 27 on a lug 28 which isrigidly connected to the setting lever 23. The helical compressionspring 26 which is supported against the rod 25 and on the annularshoulder 29 presses the lug 28 against a support ring 30 which is fixedto the rod 25. The swivel path of the setting lever 23 is restricted bytwo stops 31,32 which are seated on the adjusting screws 33,34 and cantherefore be set with great accuracy following the final assembly of thefuel injection pump.

The setting lever 23 is coupled to the adjusting lever 20 in such a waythat when the adjusting lever 20 is not operated, the setting lever 23rests against the first stop 31, and when the adjusting lever 20 ismoved over a small distance, lever 23 will come to rest against thesecond stop 32. With further movement of the adjusting lever 20 and thesetting lever 23 resting against the second stop 32, the rod 25, undercompression of the helical compression spring 26, can push through thelug 28 of the setting lever 23 so that the movement of the adjustinglever 20 is not restricted. When the setting lever 23 rests against thefirst stop 31, the lever stop 17, which is torsionally rigidly connectedwith the setting lever 23, assumes a first end position, as shown inFIG. 1. When the setting lever 23 rests against the second stop 32, thelever stop 17 is rotated in clockwise direction (FIG. 1) to the secondend position. The starting lever 13 remains pressed against the leverstop 17 by the starting spring 16 and thus follows the movement of thelever stop 17. The movement of the starting lever 13 in turn effects ashift to the right of the supply volume adjusting mechanism 11 in FIG.1, which means that the pump plunger 12 must cover a longer distanceduring the compression stroke, until the delivery orifice emerges fromthe supply volume adjusting mechanism 11. The fuel volume then injectedby the pump plunger is significantly greater than that supplied with theposition of the supply volume adjusting mechanism 11 as illustrated inFIG. 1. The stops 31,32 are now set by the adjusting screws 33,34 insuch a way that in both its end positions, the lever stop 17 forces astart lever position which in the first end position (shown in FIG. 1)sets a fuel volume as required for the hot start, and in the second endposition, sets a fuel volume as required for the cold start, thesesettings being made on the supply volume adjusting mechanism 11.

With a cold start, the driver must operate the accelerator pedal,whereby the adjusting lever 20 is rotated, which positions the settinglever 23 against the second stop 32. The supply volume adjustingmechanism 11 is moved and the fuel volume required for the cold start isset via the starting lever 13. With a hot engine start, the driver mustnot operate the accelerator pedal. The adjusting lever 20 thus assumesits basic setting, as presented in FIGS. 1 and 2, and the setting lever23 rests against the first stop 31. The lever stop 17, which is in itsfirst end position, causes the supply volume adjusting mechanism 11 toassume a sliding position on the pump plunger 12, via the starting lever13. The reduced fuel requirement for the hot start is now conditioned bythe position of the supply volume adjusting mechanism 11.

The foregoing relates to a preferred exemplary embodiment of theinvention, it being understood that other variants and embodimentsthereof are possible within the spirit and scope of the invention, thelatter being defined by the appended claims.

We claim:
 1. A fuel injection pump for internal combustion engines witha supply volume adjusting mechanism which determines the amount of fuelto be injected, a starting lever that acts on the supply volumeadjusting mechanism in order to adjust it, said starting lever beingsupported on a tensioning lever via a starting spring, with an adjustinglever which is arbitrarily operable via an accelerator pedal and whichis coupled with the tensioning lever, and with an adjustable lever stop,against which the starting lever rests, under the action of the startingspring, when the engine is not operating, the lever stop (17) isforcibly coupled with the adjusting lever (20), such that said leverstop (17) is moved by the swivelling movement of the adjusting lever(20) from its first end position into a second end position, and thatthe end positions are determined in such a way that the lever stop (17)forces a starting lever position, which in the first end position, setsa fuel volume at the supply volume adjusting mechanism (11), as requiredfor a hot start, and in the second end position, it sets a fuel volumeas required for a cold start of the engine.
 2. A fuel injection pump inaccordance with claim 1, in which the lever stop (17) assumes its firstend position with a non-operated adjusting lever (20).
 3. A fuelinjection pump in accordance with claim 1, in which for the couplingbetween lever stop (17) and adjusting lever (20), the lever stop (17) isconnected torsionally rigid with a setting lever (23) which is actuatedby the adjusting lever (20), the rotational movement of the settinglever (23) being limited by two stops (31,32) which determine the endpositions of the lever stop (17).
 4. A fuel injection pump in accordancewith claim 3, in which the setting lever (23) is pivoted on theadjusting lever (20) via a spring damped linkage (24).
 5. A fuelinjection pump in accordance with claim 3, in which the stops (31, 32)are arranged on adjusting screws (33, 34).
 6. A fuel injection pump inaccordance with claim 3, in which the setting lever (23) reststorsionally rigid on the swivel axis (18) of the lever stop (17) on theoutside of the pump housing (10).
 7. A fuel injection pump in accordancewith claim 2, in which for the coupling between lever stop (17) andadjusting lever (20), the lever stop (17) is connected torsionally rigidwith a setting lever (23) which is actuated by the adjusting lever (20),the rotational movement of the setting lever (23) being limited by twostops (31, 32) which determine the end positions of the lever stop (17).8. A fuel injection pump in accordance with claim 7, in which thesetting lever (23) is pivoted on the adjusting lever (20) via a springdamped linkage (24).
 9. A fuel injection pump in accordance with claim4, in which the stops (31, 32) are arranged on adjusting screws (33,34).
 10. A fuel injection pump in accordance with claim 7, in which thestops (31, 32) are arranged on adjusting screws (33, 34).
 11. A fuelinjection pump in accordance with claim 8, in which the stops (31, 32)are arranged on adjusting screws (33, 34).
 12. A fuel injection pump inaccordance with claim 4, in which the setting lever (23) resttorsionally rigid on the swivel axis (18) of the lever stop (17) on theoutside of the pump housing (10).
 13. A fuel injection pump inaccordance with claim 7, in which the setting lever (23) resttorsionally rigid on the swivel axis (18) of the lever stop (17) on theoutside of the pump housing (10).
 14. A fuel injection pump inaccordance with claim 8, in which the setting lever (23) resttorsionally rigid on the swivel axis (18) of the lever stop (17) on theoutside of the pump housing (10).
 15. A fuel injection pump inaccordance with claim 9, in which the setting lever (23) resttorsionally rigid on the swivel axis (18) of the lever stop (17) on theoutside of the pump housing (10).
 16. A fuel injection pump inaccordance with claim 10, in which the setting lever (23) resttorsionally rigid on the swivel axis (18) of the lever stop (17) on theoutside of the pump housing (10).
 17. A fuel injection pump inaccordance with claim 11, in which the setting lever (23) resttorsionally rigid on the swivel axis (18) of the lever stop (17) on theoutside of the pump housing (10).